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|Title: ||Biology of xanthodes graellsii (Feisth) (Lepidoptera: Noctuidae)|
|Authors: ||Dwomoh, Emmanuel Agyemang|
|Issue Date: ||13-Jun-1996|
|Series/Report no.: ||2229;|
|Abstract: ||The biology of Xanthodes graellsii (Feisth) was studied in the laboratory and the field. The number of larval instars varied from 5 to 6 but developmental period of X. graellsii (from egg to adult stage) reared in the laboratory was longer than those reared in the field. The sex of the pupa of X. graellsli can be determined by the position of genital pore on the abdomen. In the female the genital pore occurs ventrally on the 8th abdominal segment whilst in the male it is located between 8th and 9th segments.
Studies carried out on the nocturnal activities of X. graellsii revealed that adult emergence generally occurs between 1800 and 0600 and it is unimodal in distribution. The major peak for both sexes occurred after midnight.
Feeding activity of the moth began at 2000 hr and ceased at 0500 hr; two peaks of feeding activity were observed. The major peak for both sexes occurred before midnight.
Copulation occurred between 1900 and 0400 hr. Oviposition in female X. graellsii started at 1900 hr with a major peak between 1900 and 2000 hr. Two smaller peaks were observed between 2100 and 0300; 0400 and 0500.
The flight activity was determined with an insect suction trap. The combined catch for both sexes demonstrated a bimodal distribution with the major peak occurring after midnight.
Female moths were more active around midnight while male predominated in the post-midnight periods. Using the presence of spermatophore in the female bursa copulatrix as a sign of successful mating, it was observed that 2-day old male and 3-day- old female copulated successfully. Maximum mating occurred when one-day-old male was allowed to mate 3-day-old female moths.
Both male and female moths copulated once per night, however repeated matings occurred in both sexes during their life time.
Three insecticides were screened for their effectiveness in controlling X. graellsii attacking okro. Chlorpyrifos (48% EC) at 500 ml per acre applied at fortnightly interval gave the most effective protection to okro leaves than the other insecticides. Chlorpyrifos sprayed plants also provided the highest fruit yield followed by B. thuringiensis. Residual effectiveness of the three insecticides to the 3rd, 4th and 5th instar larvae of X. graellsii was evaluated by comparing percent mortality of larvae fed on treated leaves 1, 4, 9 and 14 days after insecticide application. Chlorpyrifos was found to have the highest residual effect against the three larval instars of X. graellsii. It was followed by B. thuringiensis. Irrespective of the insecticide used, it was observed that larval mortality decreased with increase in interval after insecticide application in the field.
Preliminary studies carried on the effect of planting date on the incidence of x. graensii showed that egg and Larval infestation of okro plants started as early as 4 weeks after emergence for different planting dates. It was also observed that adjusting planting dates could contribute to the reduction of egg and larval population of X. graellsii|
|Description: ||A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Philosophy in Entomology, 1996|
|Appears in Collections:||College of Agric and Natural Resources|
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